Sodium azide based suppression of fires

Abstract

A device and method device for delivering a fire suppressing gas to a space is provided. The device includes a housing disposed within the space; at least one generator disposed within the housing and containing pre-packed sodium azide based propellant; an ignition device for igniting said sodium azide based propellant and thereby generating a low-moisture fire suppressing gas; and an opening in the housing for directing the fire suppressing gas mixture into said space.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims priority under 35 U.S.C. 119(e) from U.S. Provisional Patent Application No. 60 / 873,979 filed Dec. 11, 2006.FIELD OF THE INVENTION[0002]The present invention is directed to a system and method for suppressing fires in normally occupied areas.BACKGROUND OF THE INVENTION[0003]Numerous systems and methods for extinguishing fires in a building have been developed. Historically, the most common method of fire suppression has been the use of sprinkler systems to spray water into a building for cooling the fire and wetting additional fuel that the fire requires to propagate. One problem with this approach is the damage that is caused by the water to the contents of the occupied space.[0004]The “total flood” clean agent fire protection system industry provides high value asset protection for spaces, such as computer rooms, telecommunications facilities, museums, record storage areas, and those housing power generation equip...

AI Technical Summary

Benefits of technology

[0041]Advantageously, propellants generated by sodium azide based materials are typically 10% to 15% of the temperature those generated by non-azide based propellants. For example, it is typical for sodium azide propellants to burn at approximately 400 degrees Fahrenheit and non-azide propellants to burn at approximately 3,000 degrees Fahrenheit. Thus, sodium azide based propellants require approximately only 10% to 15% of the bulk heat sink required for such non-azide based propellants. Use of sodium azide based materials therefore permits a significant reduction in size, or the inclusion of more propellant generators in a given volume.

[0052]In one embodiment, the apparatus further comprises at least one filter and screen for filtering any solid particulates and reducing the heat of the gas generated prior to the delivery of the fire suppressing gas to the normally occupied and or unoccupied space.

Problems solved by technology

One problem with this approach is the damage that is caused by the water to the contents of the occupied space.

Such design and corresponding installation work, including development of flow calculation methodologies for complex flow considerations, requires considerable up-front effort and expense.

High-pressure bottles require frequent inspection due to their propensity for leaks.

Once a leak is identified, the leaking bottle may need to be sent to a central re-filling installation, resulting in protection down time at the customer site.

As a result, fire suppression systems using Halon replacements require from two to ten times the extinguishant mass and storage space, and are therefore more costly.

Furthermore, the increased storage space required for the large increase in number of extinguishant bottles poses a difficult placement problem for facility engineers, and a considerable obstacle for those wishing to retrofit an existing Halon installation with a bottle “farm” many times bigger than its Halon predecessor in a limited storage space.

Most of these Halon alternative hydrofluorocarbons have human exposure toxicity limits very close to their required extinguishing design concentrations.

Such exposure times are typically limited to five minute or less providing occupants with reduced evacuation capability.

Occupants who are injured, aged, disabled and may also be medical patients may find this evacuation time challenging, and the increased cardio toxicity risk with many of these Halon alternative extinguishants makes limited exposure scenarios even more critical.

Hydrogen fluoride can produce a caustic acid when exposed to moisture that can pose a significant health hazard to occupants and rescue personnel, and can damage equipment.

“Environmentally friendly” alternatives to the hydrofluorocarbons have been proposed and even fielded to a limited degree, but many also suffer from their own design and operational limitations.

Even with considerable research and engineering expertise applied internationally, it has proven very difficult to design mist delivery systems for fire suppression around obstacles that are as effective as gases.

Inert gas systems, such as those using nitrogen or argon, require up to ten times the number of bottles of their Halon predecessor (due to their inefficiency and inability to be liquefied under pressure in a practical manner).

Such requires not only considerable additional storage space, but often larger diameter plumbing that would need to replace Halon-suitable pipes.

The very high pressure bottles used in inert gas systems can also pose an additional safety hazard if damaged or otherwise compromised, including the thicker-walled distribution plumbing that might be vulnerable at any joint connections.

This patent envisions delivery of a generated gas to a fire via pipes and ducts, and does not disclose any particular means by which to package the solid additive.

Furthermore, the patent does not consider the challenges in distributing an appropriate quantity of generated nitrogen gas into a habitable space and does not to consider concentrations that would reliably extinguish fires, while permitting the safe occupancy and exposure to humans for a time.

Furthermore, the extinguishant from non-azide materials is typically extremely hot, and therefore must be cooled significantly for use in normally occupied spaces.

The large mass takes up space that could be filled with additional generators, thereby reducing the overall protection space efficiency of a given cartridge container.

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